In my opinion, state machines are the best solution when you have "any arbitrarily complex combination of states and transitions, regardless of the problem doma

In my opinion, state machines are the best solution when you have "any arbitrarily complex combination of states and transitions, regardless of the problem domain, language" to quote you. However most UI state patterns are not arbitrarily complex. Mostly we're pulling a little data and there is a loading and error state. Using a state machine to manage that is perhaps a little much compared to other solutions and provokes these responses of overengineering. So it becomes the classic idea of the right tool for the job and knowing when to reach for the more powerful tool. I think that's the value of articles like this.